U.S. patent number 8,193,298 [Application Number 11/909,012] was granted by the patent office on 2012-06-05 for biodegradable aliphatic-aromatic polyesters.
This patent grant is currently assigned to Novamont S.p.A.. Invention is credited to Catia Bastioli, Giandomenico Cella, Giovanni Floridi, Andrea Scaffidi Lallaro, Tiziana Milizia, Maurizio Tosin.
United States Patent |
8,193,298 |
Bastioli , et al. |
June 5, 2012 |
Biodegradable aliphatic-aromatic polyesters
Abstract
Biodegradable aliphatic/aromatic copolyester comprising 50 to 60
mol % of an aromatic dicarboxylic acid and 40 to 50 mol % of an
aliphatic acid, at least 90% of which is a long-chain dicarboxylic
acid (LCDA) of natural origin selected from azelaic acid, sebacic
acid, brassylic acid or mixtures thereof; and a diol component.
Inventors: |
Bastioli; Catia (Novara,
IT), Milizia; Tiziana (Novara, IT),
Floridi; Giovanni (Novara, IT), Lallaro; Andrea
Scaffidi (Omegna, IT), Cella; Giandomenico
(Novara, IT), Tosin; Maurizio (Serravalle Sesia,
IT) |
Assignee: |
Novamont S.p.A. (Novara,
IT)
|
Family
ID: |
35149279 |
Appl.
No.: |
11/909,012 |
Filed: |
March 17, 2006 |
PCT
Filed: |
March 17, 2006 |
PCT No.: |
PCT/EP2006/002670 |
371(c)(1),(2),(4) Date: |
September 18, 2007 |
PCT
Pub. No.: |
WO2006/097353 |
PCT
Pub. Date: |
September 21, 2006 |
Prior Publication Data
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|
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Document
Identifier |
Publication Date |
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US 20080214702 A1 |
Sep 4, 2008 |
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Foreign Application Priority Data
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|
|
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Mar 18, 2005 [IT] |
|
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MI2005A0452 |
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Current U.S.
Class: |
528/302; 528/304;
428/480; 525/418; 525/419; 528/271; 428/77; 528/272; 428/35.1;
525/437 |
Current CPC
Class: |
C08L
67/02 (20130101); C08G 63/16 (20130101); C08L
67/02 (20130101); C08L 2666/02 (20130101); Y10T
428/29 (20150115); C08L 1/00 (20130101); C08L
67/04 (20130101); Y10T 428/1352 (20150115); C08L
3/02 (20130101); Y10T 428/31504 (20150401); Y10T
428/31786 (20150401); Y10T 428/1331 (20150115); Y10T
428/1334 (20150115); Y10T 428/249921 (20150401) |
Current International
Class: |
C08G
63/16 (20060101) |
Field of
Search: |
;528/271,272,437,302,300,303,304,305,306,308,308.1,308.3
;428/35.1,480,35.2,35.7,36.4,77,221,357,409,411.1 ;524/35,47,27
;525/418,419,437 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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0 950 678 |
|
Oct 1999 |
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EP |
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1033958 |
|
Jun 1966 |
|
GB |
|
WO 2006/097354 |
|
Sep 2006 |
|
WO |
|
Other References
European Patent Office Communication of a Notice of Opposition
dated Jan. 10, 2011, in European Patent No. 1858951 and Opposition
(Annex 1) and Document 06. cited by other .
Mattier Toledo, Operating instructions, "Density determination kit
for Excellence XP/XS analytical balancers," 2008, pp. 1-15, 72.
cited by other .
Chuah, H.H., et al., "Poly(trimethylene terephthaiate) molecular
weight and Mark-Houwink equation," Polymer, vol. 42, 2001, pp.
7137-7139. cited by other .
Gargallo, Ligia, et al., "Conformational transistion in (maleic
anhydride mono-n-octyl itaconate copolymer," Polymer Bulletin, vol.
37, 1996, pp. 553-555. cited by other .
Odian, George, "Step Polymerization," Principles of Polymerization,
John Wiley and Sons, Fourth Edition, 2004, pages 39-197. cited by
other .
Acknowledgement of Receipt and Relay under Rule 79(1) EPC dated
Aug. 4, 2011, and Experimental Report. cited by other.
|
Primary Examiner: Seidleck; James J
Assistant Examiner: Tischler; Frances
Attorney, Agent or Firm: Connolly Bove Lodge & Hutz
LLP
Claims
The invention claimed is:
1. Biodegradable aliphatic/aromatic copolyester (AAPE) comprising:
A) an acid component comprising repeating units of: 1) 50 to 60 mol
% of an aromatic polyfunctional acid; 2) 40 to 50 mol % of an
aliphatic acid, at least 90% of which is a long-chain dicarboxylic
acid (LCDA) of natural origin selected from azelaic acid, sebacic
acid, brassylic acid or mixtures thereof; B) at least one diol
component; said aliphatic long-chain dicarboxylic acid (LCDA) and
said diol component (B) having a number of carbon atoms according
to the following formula: (C.sub.LCDAY.sub.LCDA)/2+C.sub.B
Y.sub.B>7.5 where: C.sub.LCDA is the number of carbon atoms of
the LCDA and can be 9, 10 or 13; Y.sub.LCDA is the molar fraction
of each LCDA on the total number of moles of LCDA; C.sub.B is the
number of carbon atoms of each diol component; Y.sub.B is the molar
fraction of each diol on the total number of moles of the diol
component (B) said AAPE having: a biodegradability after 90 days
higher than 70%, with respect to pure cellulose according to the
Standard ISO 14855Amendment 1, a density of equal to or less than
1.2 g/cc; a number average molecular weight of 40,000-140,000; an
inherent viscosity of 0.8-1.5.
2. Biodegradable polyester according to claim 1, wherein said
aromatic dicarboxylic acid is selected from the group consisting of
the phthalic acids.
3. Biodegradable polyester according to claim 2, wherein said
aromatic dicarboxylic acid is terephthalic acid.
4. Biodegradable polyester according to claim 1, wherein the
polydispersity index M.sub.w/M.sub.n, is between 1.7 and 2.6.
5. Biodegradable polyester according to claim 4, wherein said
polydispersity index M.sub.w/M.sub.n is between 1.8 and 2.5.
6. Biodegradable polyester according to claim 1, wherein said diol
is selected from the group consisting of: 1,2-ethanediol,
1,2-propanediol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol,
1,6-hexanediol, 1,7-heptanediol, 1,8-octanediol, 1,9-nonanediol,
1,10-decanediol, 1,11-undecanediol, 1,12-dodecanediol,
1,13-tridecanediol, 1,4-cyclohexanedimethanol, propylene glycol,
neo-pentyl glycol, 2-methyl-1,3-propanediol, dianhydrosorbitol,
dianhydromannitol, dianhydroiditol, cyclohexanediol, and
cyclohexanemethanediol.
7. Biodegradable polyester according to claim 1, wherein said diol
has from 2 to 10 carbon atoms.
8. Biodegradable polyester according to claim 7, wherein said diol
has from 2 to 4 carbon atoms.
9. Biodegradable polyester according to claim 1, characterized in
that said aliphatic long-chain dicarboxylic acid (LCDA) and said
diol component (B) have a number of carbon atoms according to the
following formula:
(C.sub.LCDAY.sub.LCDA)/2+C.sub.BY.sub.B>8.
10. Biodegradable polyester according to claim 1, wherein said
biodegradability after 90 days is higher than 80%.
11. Biodegradable polyester according to claim 1, having a
crystallization temperature T.sub.c higher than 25.degree. C.
12. Biodegradable polyester according to claim 11, having a
crystallization temperature T.sub.c higher than 30.degree. C.
13. Biodegradable polyester according to claim 12, having a
crystallization temperature T.sub.c higher than 40.degree. C.
14. Biodegradable polyester according to claim 1, wherein said
aliphatic acid comprises at least one hydroxy acid in an amount of
up to 10 mol % with respect to the total molar content of the
aliphatic acid.
15. A film comprising the polyesters according to claim 1.
Description
RELATED APPLICATIONS
This application is a national stage application (under 35 U.S.C.
.sctn.371) of PCT/EP2006/002670 filed Mar. 17, 2006, which claims
benefit of Italian application MI2005A000452 filed Mar. 18, 2005,
disclosure of which are incorporated herein by reference.
The present invention relates to biodegradable aliphatic-aromatic
polyesters (AAPE) obtained from long-chain aliphatic dicarboxylic
acids, polyfunctional aromatic acids and diols, as well as to
mixtures of said polyesters with other biodegradable polymers of
natural or synthetic origin.
Biodegradable aliphatic-aromatic polyesters obtained from
dicarboxylic acids and diols are known in the literature and are
commercially available. The presence of the aromatic component in
the polyester chain is important to obtain polymers with
sufficiently high melting point and acceptable crystallization
rate.
Although polyesters of this type are currently commercially
available, the amount of aromatic acid in the chain is typically
lower than 49%, since the percentage of biodegradation of the
polyesters decreases significantly above said threshold.
It is reported in the literature (Muller et al., Angew. Chem.,
Int., Ed. (1999), 38, pp. 1438-1441) that copolymers of the
polybutylene adipate-co-terephthalate type with a molar fraction of
terephthalate of 42 mol %, biodegrade completely to form compost in
twelve weeks, whereas products with 51 mol % of molar fraction of
terephthalate show a percentage of biodegradation of less than 40%.
This different behaviour was attributed to the formation of a
higher number of butylene terephthalate sequences with a length
greater than or equal to 3, which are less easily biodegradable. If
it were possible to maintain suitable biodegradation properties, an
increase in the percentage of aromatic acid in the chain would,
however, be desirable, in so far as it would bring about an
increase in the melting point of the polyester, an increase in, or
at least a maintenance of, important mechanical properties, such as
ultimate strength and elastic modulus, and would moreover bring
about an increase in the crystallization rate of the polyester,
thereby improving its industrial processability.
A further drawback of biodegradable aliphatic-aromatic polyesters
that are currently commercially available is represented by the
fact that the monomers of which they are constituted come from
non-renewable sources, thereby maintaining a significant
environmental impact associated to the production of such
polyesters, despite their biodegradability. They have far more
energy content than LDPE and HDPE, particularly in the presence of
adipic acid. On the other hand, the use of monomers of vegetal
origin would contribute to the reduction of emission of CO.sub.2 in
the atmosphere, and to the reduction in the use of monomers derived
from non-renewable resources.
U.S. Pat. No. 4,966,959 discloses certain copolyesters comprising
from 60 to 75% mol of terephtalic acid, 25 to 40% mol of a
carboxylic aliphatic or cycloaliphatic acid, and a glycol
component. The inherent viscosity of such polyesters is from about
0.4 to about 0.6, rendering the polyesters useful as adhesives but
unsuitable for many other applications.
U.S. Pat. No. 4,398,022 discloses copolyesters comprising
terephtalic acid and 1,12-dodecanedioic acid and a glycol component
comprising 1,4-cyclohexanedimethanol. The acid component may
optionally include one or more acids conventionally used in the
production of polyesters, but the examples show that
1,12-dodecanedioic acid must be present for the polyesters to have
the desired melt strength.
U.S. Pat. No. 5,559,171 discloses binary blends of cellulose esters
and aliphatic-aromatic copolyesters. The AAPE component of such
blends comprises a moiety derived from a C.sub.2-C.sub.14 aliphatic
diacid which can range from 30 to 95% mol in the copolymer, a
moiety derived from an aromatic acid which can range from 70 to 5%
mol in the copolymer. Certain AAPEs disclosed in this document do
not require blending and are useful in film application. They
comprise a moiety derived from a C.sub.2-C.sub.10 aliphatic diacid
which can range from 95 to 35% mol in the copolymer, and a moiety
derived from an aromatic acid which can range from 5 to 65% mol in
the copolymer.
DE-A-195 08 737 discloses biodegradable AAPEs comprising
terephtalic acid, an aliphatic diacid and a diol component. The
weight average molecular weight M.sub.w of such AAPEs is always
very low (maximum 51000 g/mol), so that their industrial
applicability is limited.
It is therefore the overall object of the present invention to
disclose improved AAPEs and blends containing the same.
In fact, the present invention regards a biodegradable
aliphatic/aromatic copolyester (AAPE) comprising:
A) an acid component comprising repeating units of:
1) 50 to 60 mol % of an aromatic polyfunctional acid; 2) 40 to 50
mol % of an aliphatic acid, at least 90% of which is a long-chain
dicarboxylic acid (LCDA) of natural origin selected from azelaic
acid, sebacic acid, brassylic acid or mixtures thereof; B) at least
one diol component; said aliphatic long-chain dicarboxylic acid
(LCDA) and said diol component (B) having a number of carbon atoms
according to the following formula:
(C.sub.LCDAy.sub.LCDA)/2+C.sub.By.sub.B>7.5 where: C.sub.LCDA is
the number of carbon atoms of the LCDA and can be 9, 10 or 13;
y.sub.LCDA is the molar fraction of each LCDA on the total number
of moles of LCDA; C.sub.B is the number of carbon atoms of each
diol component; y.sub.B is the molar fraction of each diol on the
total number of moles of the diol component (B) said AAPE having: a
biodegradability after 90 days higher than 70%, with respect to
pure cellulose according to the Standard ISO 14855 Amendment 1; a
density equal to or less than 1.2 g/cc; a number average molecular
weight M.sub.n of from 40,000 to 140,000; an inherent viscosity of
from 0.8 to 1.5
Preferably, the biodegradability after 90 days as defined above is
higher than 80%.
The AAPE according to the invention is rapidly crystallisable.
Preferably, the biodegradable polyesters of the invention are
characterized in that said aliphatic long-chain dicarboxylic acid
(LCDA) and said diol component (B) have a number of carbon atoms
according to the following formula:
(C.sub.LCDAy.sub.LCDA/2)+C.sub.By.sub.B>8
By "polyfunctional aromatic acids" for the purposes of the present
invention are preferably meant aromatic dicarboxylic compounds of
the phthalic-acid type and their esters, preferably terephthalic
acid.
The content of aromatic dicarboxylic acid in the biodegradable
polyesters according to the present invention is between 50 mol %
and 60 mol % with respect to the total molar content of the
dicarboxylic acids.
The number average molecular weight M.sub.n of the polyester
according to the present invention is comprised between 40 000 and
140 000. The polydispersity index M.sub.w/M.sub.n determined by
means of gel-permeation chromatography (GPC) is between 1.7 and
2.6, preferably between 1.8 and 2.5.
Examples of diols according to the present invention are
1,2-ethandiol, 1,2-propandiol, 1,3-propandiol, 1,4-butandiol,
1,5-pentandiol, 1,6-hexandiol, 1,7-heptandiol, 1,8-octandiol,
1,9-nonandiol, 1,10-decandiol, 1,11-undecandiol, 1,12-dodecandiol,
1,13-tridecandiol, 1,4-cyclohexandimethanol, propylene glycol,
neo-pentyl glycol, 2-methyl-1,3-propandiol, dianhydrosorbitol,
dianhydroman-nitol, dianhydroiditol, cyclohexandiol, and
cyclohexan-methandiol. Particularly preferred are diols of the
C.sub.2-C.sub.10 type. Even more particularly preferred are the
C.sub.2-C.sub.4 diols. Butandiol is the most preferred one.
The polyesters according to the invention have an inherent
viscosity (measured with Ubbelhode viscosimeter for solutions in
CHCl.sub.3 of a concentration of 0.2 g/dl at 25.degree. C.) of
between 0.8 dl/g and 1.5 dl/g, preferably between 0.83 dl/g and 1.3
dl/g and even more preferably between 0.85 dl/g and 1.2 dl/g.
The Melt Flow Rate (MFR) of the polyesters according to the
invention, in the case of use for applications typical of plastic
materials (such as, for example, bubble filming, injection
moulding, foams, etc.), is between 0.5 and 100 g/10 min, preferably
between 1.5-70 g/10 min, more preferably between 2.0 and 50 g/10
min (measurement made at 190.degree. C./2.16 kg according to the
ASTM D1238 standard).
The polyesters according to the invention have a crystallization
temperature T.sub.c higher than 25.degree. C., preferably higher
than 30.degree. C. and most preferably higher than 40.degree.
C.
The polyesters have a density measured with a Mohr-Westphal
weighing machine equal to or less than 1.20 g/cm.sup.3.
The aliphatic acid A2 which can be different from LCDA can comprise
or consist of at least one hydroxy acid in an amount of up to 10
mol % with respect to the total molar content of the aliphatic
acid. Examples of suitable hydroxy acids are glycolic acid,
hydroxybutyric acid, hydroxycaproic acid, hydroxyvaleric acid,
7-hydroxyheptanoic acid, 8-hydroxycaproic acid, 9-hydroxynonanoic
acid, lactic acid or lactide. The hydroxy acids can be inserted in
the chain as such, or else can also be previously made to react
with diacids or dialcohols. The hydroxy acid units can be inserted
randomly in the chain or can form blocks of adjacent units.
In the process of preparation of the copolyester according to the
invention one or more polyfunctional molecules, in amounts of
between 0.02-3.0 mol %, preferably between 0.1 mol % and 2.5 mol %
with respect to the amount of dicarboxylic acids (as well as to the
possible hydroxy acids), can advantageously be added in order to
obtain branched products. Examples of these molecules are glycerol,
pentaerythritol, trimethylol propane, citric acid,
dipentaerythritol, monoanhydrosorbitol, monohydro-mannitol,
epoxidized oils such as epoxidized soybean oil, epoxidized linseed
oil and so on, dihydroxystearic acid, itaconic acid and so on.
Although the polymers according to the present invention reach high
levels of performance without any need to add chain extenders such
as di and/or poly isocyanates and isocyanurates, di and/or poly
epoxides, bis-oxazolines, poly carbodimides or divinylethers, it is
in any case possible to modify the properties thereof as the case
may require.
Generally such additives are used in percentages comprised between
0.05-2.5%, preferably 0.1-2.0%. In order to improve the reactivity
of such additives, specific catalysts can be used such as for
example zinc stearates (metal salts of fatty acids) for poly
epoxides.
The increase in the molecular weight of the polyesters can
advantageously be obtained, for example, by addition of various
organic peroxides during the process of extrusion. The increase in
molecular weight of the biodegradable polyesters can be easily
detected by observing the increase in the values of viscosity
following upon treatment of the polyesters with peroxides.
In case of use of the polyesters according to the present invention
for the production of films, the addition of the above mentioned
chain extenders according to the teaching of EP 1 497 370 results
in a production of a gel fraction lower than 4.5% w/w with respect
to the polyester. In this connection the content of EP 1 497 370
has to be intended as incorporated by reference in the present
description. The polyesters according to the invention possess
properties and values of viscosity that render them suitable for
use, by appropriately adjusting the molecular weight, in numerous
practical applications, such as films, injection-moulded products,
extrusion-coating products, fibres, foams, thermoformed products,
extruded profiles and sheets, extrusion blow molding, injection
blow molding, rotomolding, stretch blow molding etc.
In case of films, production technologies like film blowing,
casting, and coextrusion can be used. Moreover such films can be
subject to biorientation in line or after film production. The
films can be also oriented through stretching in one direction with
a stretching ratio from 1:2 up to 1:15, more preferably from 1:2, 2
up to 1:8. It is also possible that the stretching is obtained in
presence of an highly filled material with inorganic fillers. In
such a case, the stretching can generate microholes and the so
obtained film can be particularly suitable for hygiene
applications. In particular, the polyesters according to the
invention are suitable for the production of: films, whether
one-directional or two-directional, and multilayer films with other
polymeric materials; films for use in the agricultural sector as
mulching films; cling films (extensible films) for foodstuffs, for
bales in the agricultural sector and for wrapping of refuse; shrink
film such as for example for pallets, mineral water, six pack
rings, and so on; bags and liners for collection of organic matter,
such as collection of refuse from foodstuffs, and for gathering
mowed grass and yard waste; thermoformed single-layer and
multilayer packaging for foodstuffs, such as for example containers
for milk, yoghurt, meat, beverages, etc.; coatings obtained with
the extrusion-coating technique; multilayer laminates with layers
of paper, plastic materials, aluminium, metallized films; foamed or
foamable beads for the production of pieces formed by sintering;
foamed and semi-foamed products including foamed blocks made up of
pre-foamed particles; foamed sheets, thermoformed foamed sheets,
containers obtained therefrom for the packaging of foodstuffs;
containers in general for fruit and vegetables; composites with
gelatinized, destructured and/or complexed starch, natural starch,
flours, other fillers of natural, vegetal or inorganic origin;
fibres, microfibres, composite fibres with a core constituted by
rigid polymers, such as PLA, PET, PTT, etc. and an external shell
made with the material according to the invention, composite
fibres, fibres with various sections (from round to multilobed),
flaked fibres, fabrics and non-woven fabrics or spun-bonded or
thermobonded fabrics for the sanitary sector, the hygiene sector,
the agricultural sector, georemediation, landscaping and the
clothing sector.
The polyesters according to the invention can moreover be used in
blends, obtained also by reactive extrusion, whether with
polyesters of the same type (such as aliphatic/aromatic copolyester
as for example polybutylene tereptalate adipate PBTA, polybutylene
tereftalatesuccinate PBTS, and polybutylene tereftalateglutarate
PBTG) or with other biodegradable polyesters (for example,
polylactic acid, poly-.epsilon.-caprolactone, polyhydroxybutyrates
such as poly-3-hydroxybutyrates, poly-4-hydroxybutyrates and
polyhydroxy-butyrate-valerate, polyhydroxybutyrate-propano-ate,
polyhydroxybutyrate-hexanoate, polyhydroxybutyrate-decanoate,
polyhydroxybutyrate-dodecanoate,
polyhydroxy-butyrate-hexadecanoate,
polyhydroxybutyrate-octadecanoate, and polyalkylene succinates and
their copolymers with adipic acid, lactic acid or lactide and
caprolacton and their combinations), or other polymers different
from polyesters.
Mixtures of polyesters with polylactic acid are particularly
preferred.
According to another object of the invention, the polyesters
according to the invention can also be used in blends with polymers
of natural origin, such as for example starch, cellulose, chitosan,
alginates, natural rubbers or natural fibers (such as for example
jute, kenaf, hemp). The starches and celluloses can be modified,
and amongst these starch or cellulose esters with a degree of
substitution of between 0.2 and 2.5, hydroxypropylated starches,
and modified starches with fatty chains may, for example, be
mentioned. Preferred esters are acetates, propionates, butirrates
and their combinations. Starch can moreover be used both in its
destructurized form and in its gelatinized form or as filler.
Mixtures of polyesters with starch are particularly preferred.
Mixtures of polyesters according to the present invention with
starch can form biodegradable polymeric compositions with good
resistance to ageing and to humidity. In these compositions, which
comprise thermoplastic starch and a thermoplastic polymer
incompatible with starch, starch constitutes the dispersed phase
and the thermoplastic polymer constitutes the continuous phase. In
this connection the content of EP 947 559 has to be intended as
incorporated by reference in the present description.
The polymeric compositions can maintain a high tear strength even
in conditions of low humidity. Such characteristic is obtained when
starch is in the form of a dispersed phase with an average
dimension lower than 1 .mu.m. The preferred average numeral size of
the starch particles is between 0.1 and 0.5 microns and more than
80% of the particles have a size of less than 1 micron.
Such characteristics can be achieved when the water content of the
composition during mixing of the components is preferably kept
between 1 and 15%. It is, however, also possible to operate with a
content of less than 1% by weight, in this case, starting with
predried and pre-plasticized starch.
It could be useful also to degrade starch at a low molecular weight
before or during compounding with the polyesters of the present
invention in order to have in the final material or finished
product a starch inherent viscosity between 1 and 0.2 dl/g,
preferably between 0.6 and 0.25 dl/g, more preferably between 0.55
and 0.3 dl/g.
Destructurized starch can be obtained before of during mixing with
the polyesters of the present invention in presence of plasticizers
such as water, glycerol, di and polyglycerols, ethylene or
propylene glycol, ethylene and propylene diglycol, polyethylene
glycol, polypropylenglycol, 1,2 propandiol, trymethylol ethane,
trimethylol propane, pentaerytritol, dipentaerytritol, sorbitol,
erytritol, xylitol, mannitol, sucrose, 1,3 propandiol, 1,2,1,3,1,4
buthandiol, 1,5 pentandiol, 1,6,1,5 hexandiol,
1,2,6,1,3,5-hexantriol, neopenthil glycol, and polyvinyl alcohol
prepolymers and polymers, polyols acetates, ethoxylates and
propoxylates, particularly sorbitol ethoxylate, sorbitol acetate,
and pentaerytritol acetate. The quantity of high boiling point
plasticizers (plasticizers different from water) used are generally
from 0 to 50%, preferably from 10 to 30% by weight, relative to
starch.
Water can be used as a plasticizer in combination with high boiling
point plasticizers or alone during the plastification phase of
starch before or during the mixing of the composition and can be
removed at the needed level by degassing in one or more steps
during extrusion. Upon completion of the plastification and mixing
of the components, the water is removed by degassing to give a
final content of about 0.2-3% by weight.
Water, as well as high-boiling point plasticizers, modifies the
viscosity of the starch phase and affects the rheological
properties of the starch/polymer system, helping to determine the
dimensions of the dispersed particles. Compatibilizers can be also
added to the mixture. They can belong to the following classes:
Additives such as esters which have hydrophilic/lipophilic balance
index values (HLB) greater than 8 and which are obtained from
polyols and from mono or polycarboxylic acids with dissociation
constants pK lower than 4.5 (the value relates to pK of the first
carboxyl group in the case of polycarboxylic acids.) Esters with
HLB values of between 5.5 and 8, obtained from polyols and from
mono or polycarboxylic acids with less than 12 carbon atoms and
with pK values greater than 4.5 (this value relates to the pK of
the first carboxylic group in the case of polycarboxylic acids).
Esters with HLB values lower than 5.5 obtained from polyols and
from fatty acids with 12-22 carbon atoms.
These compatibilizers can be used in quantities of from 0.2 to 40%
weight and preferably from 1 to 20% by weight related to the
starch. The starch blends can also contain polymeric
compatibilizing agents having two components: one compatible or
soluble with starch and a second one soluble or compatible with the
polyester.
Examples are starch/polyester copolymers through
transesterification catalysts. Such polymers can be generated
trough reactive blending during compounding or can be produced in a
separate process and then added during extrusion. In general block
copolymers of an hydrophilic and an hydrophobic units are
particularly suitable. Additives such as di and polyepoxides, di
and poly isocyanates, isocyanurates, polycarbodiimmides and
peroxides can also be added. They can work as stabilizers as well
as chain extenders.
All the products above can help to create the needed
microstructure. It is also possible to promote in situ reactions to
create bonds between starch and the polymeric matrix. Also
aliphatic-aromatic polymers chain extended with aliphatic or
aromatic diisocyanates or di and polyepoxides or isocyanurates or
with oxazolines with intrinsic viscosities higher than 1 dl/9 or in
any case aliphatic-aromatic polyesters with a ratio between Mn and
MFI at 190.degree. C., 2.16 kg higher than 10 000, preferably
higher than 12 500 and more preferably higher than 15 000 can also
be used to achieve the needed microstructure.
Another method to improve the microstructure is to achieve starch
complexation in the starch-polyester mixture.
In this connection the content of EP 965 615 has to be intended as
incorporated by reference in the present description. In such a
case, in the X-Ray spectra of the compositions with the polyester
according to the present invention, the Hc/Ha ratio between the
height of the peak (Hc) in the range of 13-14.degree. of the
complex and the height of the peak (Ha) of the amorphous starch
which appears at about 20.5.degree. (the profile of the peak in the
amorphous phase having been reconstructed) is less than 2 and
greater than 0.02.
The starch/polyester ratio is comprised in the range 5/95% weight
up to 60/40% by weight, more preferably 10/90-45/55% by weight. In
such starch-based blends in combination with the polyesters of the
present invention it is possible to add polyolefins, polyvynil
alcohol at high and low hydrolysis degree, ethylene vinylalcohol
and ethylene vinylacetate copolymers and their combinations as well
as aliphatic polyesters such as polybuthylensuccinate,
polybuthylensuccinate adipate, polybuthylensuccinate
adipate-caprolactate, polybuthylensuccinate-lactate,
polycaprolactone polymers and copolymers, PBT, PET, PTT,
polyamides, polybuthylen terephtalate adipates with a content of
terephtalic acid between 40 and 70% with and without solfonated
groups with or without branchs and possibly chain extended with
diisocianates or isocianurates, polyurethanes, polyamide-urethanes,
cellulose and starch esters such as acetate, propionate and
butyrrate with substitution degrees between 1 and 3 and preferably
between 1.5 and 2.5, polyhydroxyalkanoates, poly L-lactic acid,
poly-D lactic acid and lactides, their mixtures and copolymers.
The starch blends of the polyesters of the present invention
maintain a better ability to crystallize in comparison with
compostable starch blends where copolyester are polybuthylen
adipate terephtalates at terephtalic content between 45 and 49%
(range of the product with industrial performances) and can be
easily processable in film blowing even at MFI (170.degree. C., 5
kg) of 7 g/10 min due to the high crystallization rate of the
matrix. Moreover they have impact strength higher than 20 kj/m2,
preferably higher than 30 kj/m2 and most preferably higher than 45
kj/m2 (measured on blown film 30 um thick at 10.degree. C. and less
then 5% relative humidity). Particularly resistant and easily
processable compounds contain destructurized starch in combination
with the polyesters of the invention and polylactic acid polymers
and copolymers with and without additives such as polyepoxydes,
carbodiimmides and/or peroxides.
The starch-base films can be even transparent in case of
nanoparticles of starch with dimensions lower than 500 .mu.m and
preferably lower than 300 .mu.m.
It is also possible to go from a dispersion of starch in form of
droplets to a dispersion in which two co-continuous phases coexist
and the blend is characterized for allowing a higher water content
during processing.
In general, to obtain co-continuous structures it is possible to
work either on the selection of starch with high amylopectine
content and/or to add to the starch-polyester compositions block
copolymers with hydrophobic and hydrophilic units. Possible
examples are polyvynilacetate/polyvinylalcohol and
polyester/polyether copolymers in which the block length, the
balance between the hydrophilicity and hydrophobicity of the blocks
and the quality of compatibilizer used can be suitably changed in
order to finely adjust the microstructure of the starch-polyester
compositions.
The polyesters according to the invention can also be used in
blends with the polymers of synthetic origin and polymers of
natural origin mentioned above. Mixtures of polyesters with starch
and polylactic acid are particularly preferred.
Blends of the polyesters according the present invention with PLA
are of particular interest because the high crystallization rate of
the aliphatic-aromatic polyesters of the invention and their high
compatibility with PLA polymers and copolymers permits to cover
materials with a wide range of rigidities and high speed of
crystallization which makes these blends particularly suitable for
injection molding and extrusion.
Moreover, blends of such polyesters with poly L-lactic acid and
poly D-lactic acid or poly L-lactide and D-lactide where the ratio
between poly L- and poly D-lactic acid or lactide is in the range
10/90-90/10, preferably 20/80-80/20, and the ratio between
aliphatic-aromatic polyester and the polylactic acid or PLA blend
is in the range 5/95-95/5, preferably 10/90-90/10, are of
particular interest for the high crystallization speed and the high
thermal resistance. Polylactic acid or lactide polymers or
copolymers are generally of molecular weight Mn in the range
between 30 000 and 300 000, more preferably between 50 000 and 250
000.
To improve the transparency and thoughness of such blends and
decrease or avoid a lamellar structure of polylactide polymers, it
is possible to introduce other polymers as compatibilizers or
toughening agents such as: polybuthylene succinate and copolymers
with adipic acid and or lactic acid and or hydroxyl caproic acid,
polycaprolactone, aliphatic polymers of diols from C2 to C13 and
diacids from C4 to C13, polyhydroxyalkanoates, polyvynilalcohol in
the range of hydrolysis degree between 75 and 99% and its
copolymers, polyvynilacetate in a range of hydrolysis degree
between 0 and 70%, preferably between 0 and 60%. Particularly
preferred as diols are ethylene glycol, propandiol, butandiol and
as acids: azelaic, sebacic, undecandioic acid, dodecandioic acid,
brassylic acid and their combinations.
To maximize compatibility among the polyesters of the invention and
polylactic acid it is very useful the introduction of copolymers
with blocks having high affinity for the aliphatic-aromatic
copolyesters of the invention, and blocks with affinity for the
lactic acid polymers or copolymers. Particularly preferred examples
are block copolymers of the aliphatic aromatic copolymers of the
invention with polylactic acid. Such block copolymers can be
obtained taking the two original polymers terminated with hydroxyl
groups and then reacting such polymers with chain extenders able to
react with hydroxyl groups such as diisocyanates. Examples are 1.6
esamethylendiisocyanate, isophorondiisocyanate,
methylendiphenildiisocyanate, toluendiisocyanate or the like. It is
also possible to use chain extenders able to react with acid groups
like di and poly epoxides (e.g. bisphenols diglycidyl ethers,
glycerol diglycidyl ethers) divinyl derivatives if the polymers of
the blend are terminated with acid groups. It is possible also to
use as chain extenders carbodiimmides, bis-oxazolines,
isocyanurates etc.
The intrinsic viscosity of such block copolymers can be between 0.3
and 1.5 dl/g, more preferably between 0.45 and 1.2 dl/g. The amount
of compatibilizer in the blend of aliphatic-aromatic copolyesters
and polylactic acid can be in the range between 0.5 and 50%, more
preferably between 1 and 30%, more preferably between 2 and 20% by
weight.
The polyesters according to the present invention can
advantageously be blended also with filler both of organic and
inorganic nature. The preferred amount of fillers is in the range
of 0.5-70% by weight, preferably 5-50% by weight.
As regards organic fillers, wood powder, proteins, cellulose
powder, grape residue, bran, maize husks, compost, other natural
fibres, cereal grits with and without plasticizers such as polyols
can be mentioned.
As regards inorganic fillers, it can be mentioned substances that
are able to be dispersed and/or to be reduced in lamellas with
submicronic dimensions, preferably less than 500 nm, more
preferably less than 300 nm, and even more preferably less than 50
nm. Particularly preferred are zeolites and silicates of various
kind such as wollastonites, montmorillonites, hydrotalcites also
functionalised with molecules able to interact with starch and or
the specific polyester. The use of such fillers can improve
stiffness, water and gas permeability, dimensional stability and
maintain transparency.
The process of production of the polyesters according to the
present invention can be carried out according to any of the
processes known to the state of the art. In particular the
polyesters can be advantageously obtained with a polycondensation
reaction.
Advantageously, the process of polymerization of the copolyester
can be conducted in the presence of a suitable catalyst. As
suitable catalysts, there may be mentioned, by way of example,
metallo-organic compounds of tin, for example derivatives of
stannoic acid, titanium compounds, for example orthobutyl titanate,
and aluminium compounds, for example triisopropyl aluminium,
antimony compounds, and zinc compounds.
EXAMPLES
In the examples provided hereinafter, the following test methods
were adopted: MFR was measured in the conditions envisaged by the
ASTM D 1238-89 standard at 150.degree. C. and 5 kg or at
190.degree. C. and 2.16 kg; the melting and crystallization
temperatures and enthalpies were measured with a differential
scanning calorimeter Perkin Elmer DSC7, operating with the
following thermo profile: 1st scan from -30.degree. C. to
200.degree. C. at 20.degree. C./min 2nd scan from 200.degree. C. to
-30.degree. C. at 10.degree. C./min 3rd scan from -30.degree. C. to
200.degree. C. at 20.degree. C./min T.sub.m1 was measured as
endothermic-peak value of the 1st scan, and T.sub.m2 as that of the
3rd scan; T.sub.c was measured as exothermic-peak value of the 2nd
scan. Density
Determination of Density according to the Mohr Westphal method was
performed with an analytical balance Sartorius AC 120S equipped
with a Sartorius Kit YDK 01. The Kit was provided with two small
baskets. Once the Kit had been mounted, ethanol was introduced in
the crystallizer. The balance was maintained at room
temperature.
Each test was performed with about 2 g of polymer (one or more
pellets).
The density d was determined according to the formula below:
D=(W.sub.a/G)d.sub.f1 where W.sub.a: weight of the sample in air
W.sub.f1: weight of the sample in alcohol G=W.sub.a-W.sub.f1
d.sub.f1=ethanol density at room temperature (Values read on tables
provided by the company Sartorius with the Kit).
The experimental error of the Density values was in the range of
.+-.2.5.times.10.sup.-3. .eta..sub.in has been determined according
to the ASTM 2857-87 method M.sub.n has been determined on a Agilent
1100 Series GPC system, with chloroform as eluent and polystyrene
standards for the calibration curve".
Example 1
A 25-1 steel reactor, provided with a mechanical stirrer, an inlet
for the nitrogen flow, a condenser, and a connection to a vacuum
pump was charged with: 2890 g of terephthalic acid (17.4 mol), 3000
g of sebacic acid (14.8 mol), 3500 g butandiol (38.9 mol), 6.1 g of
butylstannoic acid.
The molar percentage of terephthalic acid with respect to the sum
of the moles of the acid components was 54.0 mol %.
The temperature of the reactor was then increased up to 200.degree.
C., and a nitrogen flow was applied. After approximately 90% of the
theoretical amount of water had been distilled, the pressure was
gradually reduced to a value of less than 3 mmHg, and the
temperature was raised to 240.degree. C.
After approximately 3 hours, the molten product was poured from the
reactor, cooled in a water bath and granulated. During the latter
operations it was possible to note how the product starts to
solidify rapidly and can be easily granulated. The product obtained
had an inherent viscosity (measured in chloroform at 25.degree. C.,
c=0.2 g/dl) .eta..sub.in=0.93 (dl/g), MFR (190.degree. C., 2.16
kg)=20 g/10 min, M.sub.n=52103 and a density of 1.18
g/cm.sup.3.
From H-NMR analysis a percentage of aromatic units was found of
53.5.+-.0.5%.
Example 1A
The reactor as per Example 1 was charged with the same ingredients
of Example 1: 2890 g of terephthalic acid (17.4 mol), 3000 g of
sebacic acid (14.8 mol), 3500 g butandiol (38.9 mol), 6.1 g of
butylstannoic acid.
The molar percentage of terephthalic acid with respect to the sum
of the moles of the acid components was 54.0 mol %.
The reaction has been carried out for the time necessary to obtain
a product having an inherent viscosity (measured in chloroform at
25.degree. C., c=0.2 g/dl) .eta..sub.in=1.03 (dl/g), MFR
(190.degree. C., 2.16 kg)=14.8 g/10 min, M.sub.n=58097 and a
density of 1.18 g/cm.sup.3.
Example 2
Comparison
The reactor as per Example 1 was charged with: 2480 g of
terephthalic acid (14.9 mol), 3400 g of sebacic acid (16.8 mol),
3430 g butandiol (38.1 mol), 6.1 g of butylstannoic acid.
The molar percentage of terephthalic acid with respect to the sum
of the moles of the acid components was 47 mol %.
The temperature of the reactor was then raised to 200.degree. C.,
and a nitrogen flow was applied. After approximately 90% of the
theoretical amount of water had been distilled, the pressure was
reduced gradually until a value of less than 3 mmHg was reached,
and the temperature was raised up to 240.degree. C.
After approximately 3 hours, a product was obtained with inherent
viscosity (measured in chloroform at 25.degree. C., c=0.2 g/dl)
.eta..sub.in=1.00 (dl/g) and MFR (190.degree. C., 2.16 kg)=13 g/10
min.
From H-NMR analysis, a percentage of aromatic units of 47.0.+-.0.5%
was found.
Example 3
Comparison
The reactor as per Example 1 was charged with: 2770 g of dimethyl
terephthalate (14.3 mol), 3030 g of dimethyl adipate (17.4 mol),
3710 g of butandiol (41.2 mol), 0.7 g of tetraisopropyl
orthotitanate (dissolved in n-butanol)
The molar percentage of aromatic content with respect to the sum of
the moles of the acid components was 45 mol %.
The temperature of the reactor was then increased to
200-210.degree. C. After at least 95% of the theoretical amount of
methanol had been distilled, the pressure was gradually reduced
until a value of less than 2 mmHg was reached, and the temperature
was raised to 250-260.degree. C.
After approximately 4 hours, a product was obtained with inherent
viscosity (measured in chloroform at 25.degree. C., c=0.2 g/dl)
.eta..sub.in=0.92 (dl/g) and MFR (190.degree. C., 2.16 kg)=20 g/10
min.
From H-NMR analysis, a percentage of aromatic units of 47.0.+-.0.5%
was found.
Example 4
Comparison
The process of Example 1 was repeated with: 3623.9 g of dimethyl
terephthalate (18.68 mol), 3582.5 g of butandiol (39.81 mol),
2244.7 g of azelaic acid (11.94 mol).
The molar percentage of aromatic content with respect to the sum of
the moles of the acid components was 61 mol %.
A product was obtained with inherent viscosity (measured in
chloroform at 25.degree. C., c=0.2 g/dl) .eta..sub.in=0.95 (dl/g),
density 1.21 g/cc and MFR (190.degree. C., 2.16 kg)=5.5 g/10
min.
Example 5
The process of Example 1 was repeated with: 3476.48 g of dimethyl
terephthalate (17.92 mol), 3493.80 g of butandiol (38.82 mol), 2411
g of sebacic acid (11.94 mol).
The molar percentage of aromatic content with respect to the sum of
the moles of the acid components was 60 mol %.
A product was obtained with M.sub.n=56613, M.sub.w/M.sub.n=2.0364
inherent viscosity (measured in chloroform at 25.degree. C., c=0.2
g/dl) .eta..sub.in=0.97 (dl/g), density 120 g/cc and MFR
(190.degree. C., 2.16 kg)=7.8 g/10 min.
Example 6
The process of Example 1 was repeated with: 3187.4 g of dimethyl
terephthalate (16.43 mol), 3559.1 g of butandiol (39.55 mol),
2630.1 g of azelaic acid (14.00 mol).
The molar percentage of aromatic content with respect to the sum of
the moles of the acid components was 54 mol %.
A product was obtained with inherent viscosity (measured in
chloroform at 25.degree. C., c=0.2 g/dl) .eta..sub.in=1.04 (dl/g),
density=1.2 g/cc and MFR (190.degree. C., 2.16 kg)=7.12 g/10
min.
Example 7
The process of Example 1 was repeated with: 2865.4 g of dimethyl
terephthalate (14.77 mol), 3201.1 g of butandiol (35.57 mol), 3072
g of brassylic acid (12.6 mol).
The molar percentage of aromatic content with respect to the sum of
the moles of the acid components was 54 mol %.
A product was obtained with inherent viscosity (measured in
chloroform at 25.degree. C., c=0.2 g/dl) .eta..sub.in=0.90 (dl/g),
density=1.16 g/cc and MFR (190.degree. C., 2.16 kg)=g/10 min.
The specimens of the above examples were then filmed with the
blow-film technique, on a Formac Polyfilm 20 apparatus, equipped
with metering screw 20C13, L/D=25, RC=1.3; air gap 1 mm; 30-50 RPM;
T=140-180.degree. C. The films thus obtained had a thickness of
approximately 30 .mu.m.
A week after filming, and after conditioning at 23(?).degree. C.,
with 55% relative humidity, the tensile properties were measured
according to the ASTM D882-88 standards.
Listed in Table 1 are the thermal properties of the products of the
examples, whilst Table 2 lists the mechanical properties of the
films obtained from such products.
TABLE-US-00001 TABLE 1 Thermal properties Example Aromatic T.sub.m1
.DELTA.H.sub.m1 T.sub.c .DELTA.H.sub.c T.sub.m2 1 53.5% 133 28 58
20 130 1A 53.5 -- -- 46 19 129 2 (comp.) 47% 112 19 22 19 113 3
(comp.) 47% 120 19 16 18 114 4 (comp) 61% -- -- 104 21 154 5 60% --
-- 82 23 145 6 54% -- -- 42 24 130 7 54% -- -- 76 16 133
TABLE-US-00002 TABLE 2 Mechanical properties Tensile EXAMPLE
properties - 2 3 4 longitudinal 1 (comp) (comp) (comp) 5 6 7* Yield
point 11 6.5 9 11.5 12 9 6 (MPa) Ultimate 40 28 40 40.0 45 33.5
23.5 strength (MPa) Elastic 90 65 105 170 130 120 70 modulus (MPa)
Failure energy 143 135 170 150 154 169 155 (MJ/m.sup.3) *The
mechanical properties of the product of example 7 were tested on a
compression molded sample with a thickness of about 100 .mu.m.
Biodegradation Test
For the products of Table 3 the biodegradation test was carried out
in controlled composting according to the Standard ISO 14855
Amendment 1.
The tests were carried out on 30-micron films ground in liquid
nitrogen until they were fragmented to a size of less than 2 mm, or
on pellets ground to particles having diameter <250 .mu.m. As
positive control microcrystalline cellulose Avicel.RTM. for column
chromatography No. K29865731 202 was used. Powder grain size: 80%
between 20 .mu.m 160 .mu.m; 20% less than 20 .mu.m.
TABLE-US-00003 TABLE 3 BIODEGRADATION Relative Aromatic LCDA/
Particles biodegradation Example content Diol ground from after 90
days 1 53.5% Sebacic Film 107.44 Butandiol 2 (comp.) 47% Sebacic
Film 99.6 Butandiol 3 (comp.) 47% Adipic Film 80.71 Butandiol
Cellulose -- -- Film/ 100 pellets 4 (comp.) 61% Azelaic pellets
10.39 Butandiol (end of the test: 49 days) 5 60% Sebacic pellets
104 Butandiol 6 54% Azelaic pellets 82 Butandiol 7 54% Brassilic
pellets 73 Butandiol
TABLE-US-00004 TABLE 4 DENSITY Aromatic Density Example content
LCDA/Diol g/cc 1 53.5% Sebacic/Butandiol 1.18 2 (comp.) 47
Sebacic/Butandiol 1.17 3 (comp.) 47% Adipic/Butandiol 1.23 4
(comp.) 61% Azelaic/Butandiol 1.21 5 60% Sebacic/Butandiol 1.20 6
54% Azelaic/Butandiol 1.20 7 54% Brassylic/Butandiol 1.15
It appears from the examples above that the selection of AAPEs
according to the present invention provides products having an
excellent balance of biodegradability and mechanical
properties.
Example 8
28 parts by weight of the polymer of example 6 were blended with 58
parts of poly L-lactide polymer having a Mn of 180000, MFR at
190.degree. C., 2.16 kg of 3.5 g/10 min, a residue of lactide less
than 0.2% and a D content of about 6%, and 14 parts of talc. The
extruder used was a twin screw extruder Haake Rheocord 90 Rheomex
TW-100. The thermal profile was ranging between 120 and 190.degree.
C.
The pellets obtained have been dried for 1 hour at 60 C. The melt
viscosity was of 600 Pa*s, measured at 190.degree. C. and shear
rate of 100 sec-1 in a capillary rheometer Goettfert Rheotester
1000 equipped with a capillary rheometer of 1 mm. The pellets have
been injection molded in a Sandretto Press 60 Series 7 using a
dumbbell mold for the production of samples for mechanical testing
and a 12 cavity clipper mold to test the industrial
moldability.
The mechanical properties obtained on dumbbell samples according to
the ASTM norm D638, after conditioning at 23.degree. C., 55% RH are
reported below:
Stress at break (MPa) 42
Elongation at break (%) 271
Young Modulus (MPa) 2103
Energy at break (Kj/m2) 1642
The dumbbell samples have been tested in biodegradation under
controlled composting obtaining 100% of biodegradation in 50 days.
The processing cycles are comparable to polypropilene and are of 14
seconds and the molding system is perfectly automatic.
A blend different from the one described in this example just for
the aromatic-aliphatic polyester, particularly the polymer of
example 6 is replaced with poly buthylen adipate terephtalate MFR
3.4 at 190.degree. C., 2.16 kg, terephtalic acid 47% mole and
density of 1.23 g/cm3 the molded parts could not be demolded
automatically.
Example 9
A blend has been made mixing 70% by weight of the polymer of
example 5 and 30% by weight of the same PLA described in example 8.
The blend has been produced in the twin screw extruder of example 8
with the same thermal profile. The pellets have been dried and have
been film blown as reported in the previous examples.
The film has shown the following tensile performances in the film
direction: Stress at break (MPa) 25 Elongation at break (%) 400
Young Modulus (MPa) 590 Energy at break (Kj/m2) 3600
The film had a good transparency. The tear strength was different
in the two directions of film blowing showing a significant
orientation.
The addition of 10% of a block copolymer of PLA and an aliphatic
aromatic block constituted by butandiol with sebacic and
terephtalic acid in a ratio 46-54% by mole, having 0.85 dl/g of
viscosity gave tensile properties similar and better than the
sample without compatibilizer (Stress at break (MPa) 28, Elongation
at break (%) 380, Young Modulus (MPa) 840, Energy at break (Kj/m2)
3600) but the tear strength was more balanced in the two
directions.
* * * * *